The present application relates to transport of substrates such as silicon wafers within a facility that includes multiple substrate processing tools.
Processing of semiconductor substrates (wafers) such as silicon wafers is used to fabricate a variety of integrated circuits (ICs) in what may be referred to as a “fab.” Fabs are extremely expensive to build and operate. Special equipment may be required to maintain a clean room environment (e.g. special air-handling to reduce the number of airborne particles). Reducing the area of a fab reduces construction cost and operating cost. In some cases, a fab has a main floor where processing tools are arranged with space for personnel access around each tool (e.g. for maintenance) and a wafer loading area in front of each tool. Passageways for personnel and wafer transport may take significant space within a fab.
A semiconductor device manufacturing line may include multiple semiconductor substrate processing tools that perform various processes, such as film deposition like sputtering and CVD (Chemical Vapor Deposition), exposure, etching, rinsing, and CMP (Chemical Mechanical Polishing) on semiconductor substrates (wafers). A substrate transport system may carry the wafers between semiconductor processing tools in an enclosure such as a FOUP (Front-Opening Unified Pod) or other substrate transport pod.
In a current FOUP transfer system, a load port of a FOUP is provided at a front part of a semiconductor processing tool (e.g. a tool such as a cluster tool), at about the same height as a worker's waist. This is because the transfer interface is designed ergonomically for human-centered operation (i.e. the height of the load port is designed to allow manual loading and or manual assistance or maintenance of the load port). A load port may be an assembly that provides a clean environment for opening FOUPs and for transfer of the substrates in the FOUP to the semiconductor processing equipment. Various mechanical components of the load port may facilitate handling of the FOUP and the substrates.
The following problems may occur when a FOUP transfer is carried out by using the FOUP transfer system as described above.                (1) The FOUP has to be transferred for a few meters (see pathway A1 in FIG. 1) from a ceiling transfer rail to the load port placed at the front part of the semiconductor processing equipment. Due to this, the transfer mechanism to transfer the wafers from the overhead rail to the process chamber may be large, complicated, expensive, and transfer time may be long.        (2) Significant space is generally dedicated for the load port at the front of the equipment (see region R0) which may be wasteful of valuable clean room space (i.e. the load port may have a significant footprint in addition to the footprint of the semiconductor processing equipment). Because each piece of semiconductor processing equipment may require one or more such load port (e.g. two or more load ports to provide a constant supply of wafers throughout FOUP transfers), the aggregated footprints of such equipment may represent a significant area and thus may represent a significant cost.        (3) Movement of FOUPs along rails means that if the rail become blocked (e.g. a FOUP becomes jammed, some other object obstructs the rails, or rails become deformed, then delivery of FOUPs stops until human intervention unblocks the rail).        (4) Significant space may be dedicated to providing personnel access around semiconductor substrate processing tools to allow human operation, loading, and maintenance to be carried out. This is in addition to space required for FOUP loaders.        